Metals normally are quite reactive and readily oxidized under the proper conditions. Thus for example, iron readily reacts with oxygen to form the various oxides of iron in the presence of hydrogen ion, normally as provided by water. Other metals such as alminum, cobalt, chromium and nickel are also highly reactive and the surfaces of these metals are normally covered with an oxide coating. Although these metals are normally considered as corrosion resistant as compared, for example, to iron, it is in fact their high reactivity that provides this property as the oxides of these metals are relatively inert and thus create a protective coating over the metal which gives the metal its corrosion resistance.
The oxide coatings, however, can be a serious problem if it is desired to modify or enhance the surface of the metal by providing a coating thereover. For example, if a decorative coating is applied to the metal surface over the substantially nonreactive oxide coating, the coating may not adhere properly and in fact can make metal corrosion worse than if the surface were uncoated. In other applications it may be desired to apply lubricant coatings over a metal surface, as is the case in magnetic recording media such as discs and recording tape. Such articles normally employ a cobalt or nickel metal surface for the magnetic imprinting of data and the like. These surfaces are then brought in close proximity or contact with a slider head for imprinting or playing back the magnetic information. The relative proximate contact between the slider head and the magnetic surface can produce severe wear on the surfaces of both the slider head and the magnetic recording media. Various lubricating compositions have been employed in the prior art as coatings over the surface of the recording media to reduce wear. If these coatings are applied without some chemical bonding between the coating material and the surface of the recording media, the lubricant film is quickly worn away and the lubricity lost.
Yet another problem is encountered in connection with the uniformity of the surface of the metal product after manufacturing. For example, it is highly desirable to provide as uniform a surface as possible for recording media. The substrate of such recording media, particularly for recording discs, is often aluminum over which is deposited nickel and cobalt coatings. The substrate material is normally first machined to remove surface imperfections and then subjected to the subsequent operations to provide the magnetic coatings thereon. It has been found, however, that when machining metal substrates such as aluminum in the presence of cutting fluids, there are reactions occurring between the cutting fluids and the reactive aluminum surface to produce reaction byproducts which adhere to the metal surface. These reaction byproducts interfere with subsequent coating or surface preparations and are ordinarily sloughed off during the subsequent operations to produce pin holes or imperfections in the overcoating layers or produce pitting of the substrate surface which seriously interferes with the creation of a highly uniform finished surface for the recording medium.